Fluorescent lampholders with breakage resistant plunger stop arrangement



w. H. HENSHAW, JR 3,329,924 FLUORESCENT LAMPHOLDERS WITH BRBAKAGERESISTANT PLUNGER STOP ARRANGEMENT July 4, 1967 Filed June '7, 1965 2Sheets-Sheet 1 I Attarwqg.

y 4, 1967 w. H. HENSHAW, JR 3,

FLUORESCENT LAMPHOLDERS WITH BREAKAGE RESISTANT PLUNGER STOP ARRANGEMENTFiled June 7, 1965 2 Sheets-Sheet 2 4 orwey United States Patent3,329,924 FLUORESCENT LAMPHOLDERS WITH BREAK- AGE RESISTANT PLUNGER STOPARRANGE- NIENT Wallace H. Henshaw, Jr., Trumbull, Conn., assignor toGeneral Electric Company, a corporation of New York Filed June 7, 1965,Ser. No. 461,846 11 Claims. (Cl. 339-52) This invention relatesgenerally to electric wiring devices and more particularly tolampholders for mounting gaseous discharge lamps such as fluorescentlamps.

In order to support an elongated fluorescent lamp of the high outputtype, it is customary to provide a pair of lampholders. One of thelampholders with a retractable spring-biased plunger, generally referredto as the telescopic lampholder is used to support the fluorescent lampat one end while a lampholder of the fixed type is used at the otherend. With such a set of lampholders, it is possible to mount thefluorescent lampby inserting one end of the lamp into the lampholderwith the springbiased plunger and depressing the plunger until the otherend of the lamp can be inserted into the other lampholder of the set.With the lamp engaged between the lampholders, a resilient support isprovided for the fluorescent lamp. The lampholders also serve as socketsfor energizing the lamps from a fluorescent lamp ballast.

lit will be appreciated that considerable length of travel is requiredfor the plunger of the telescopic lampholder. When the spring-biasedplunger is pushed inwardly, one or a pair of springs is being compressedas the plunger travels into the cavity of the lampholder. If the springbiased plunger is released from its retracted position, the springforces the plunger outwardly. A boss on the plunger engages a flangeformed in the lampholder housing and thereby stops the plunger in itsextended position.

In conventional plunger stop arrangements a sudden release of theplunger from its retracted position not too infrequently causes the bossor the flange of the lampholder to break thereby causing permanentdamage to the lampholder. Thus, such conventional arrangement forstopping the travel of a retractable plunger have not been entirelysatisfactory in practice because of the susceptibility to breakage.Further, materials commonly used to fabricate the lampholder plunger andhousing are the phenolic and urea-formaldehyde resins which have arelatively hard and low impact strength. Although more expensivematerials are available with more suitable strength properties, it hasnot been commercially desirable to use these materials because of theadded cost to the end product.

Accordingly, a general object of my invention is to provide a new andimproved telescopic lampholder construction.

A more specific object of my invention is to provide a new and improvedlampholder wherein possible breakage of the lampholder parts, when theplunger is suddenly released from its retracted position, issubstantially reduced.

In accordance with one form of my invention I have provided a lampholderembodying an improved arrangement for stopping a retractable plungerwhen it is suddenly-released from a retracted position. In thelampholder, which I have used to illustrate my invention, the lampholderhousing is formed with a plunger-receiving chamber member. A contactsupport plunger or member is slidably mounted within theplunger-receiving chamber member for movement between an extendedposition and a retracted position. At least two or more slots areprovided in one of the members, either the contact support member or theplunger-receiving member, and an equal number of slot-engagingprojections are provided on the other member to guide the movement ofthe plunger member from the retracted position to the extend positionand vice versa.

Each elongated slot and slot-engaging projection is formed with a frontend portion. When an associated pair of front end portions is engaged,the spring-biased movement of the contact support member from aretracted position is stopped. At least one front end portion of anassociated pair of front end portions includes a slanted or inclinedsurface. The other front end portion of the associated pair of front endportions includes an impact part. The impact part is arranged withrespect to its associated slanted surface so that whenever the contactsupport member is suddenly released from its retracted position, oneimpact part will initially strike its associated slanted surface todeflect the movement of the contact support member. The impact part ofanother associated pair of front end portions then strikes itsassociated slanted surface to effect another deflection of movement ofthe contact support member before it is finally stopped in the extendedposition. Preferably, at least two such deflections should normally beproduced to minimize the impact produced by the contact support memberstriking the lampholder housing.

An important advantage resulting from the improved plunger stoparrangement is that breakage of lampholder components is substantiallyreduced. The assembly of the lampholder may require that the plunger bedepressed to a retracted position in order to facilitate installing thelampholder on the fixture and breakage frequently occurs duringassembly. The improved arrangement is particularly advantageous inreducing breakage while lampholders are assembled on fluorescent lampfixtures. Also, with the improved arrangement it is possible to reducebreakage that occurs when the lamp is suddenly removed from a lampholderand the plunger is suddenly released from its retracted position.

Further aspects of my invention will become apparent upon considerationof the following more detailed description. The subject matter which Iregard as my invention is set forth in the appended claims. Theinvention, however, together with further objects and advantages thereofmay be best understood by referring to the following description takenin conjunction with the accompanying drawings in which:

FIGURE 1 is a side elevational view showing one end of a fluorescentlamp supported in a telescopic lampholder embodying one form of theinvention, the retractable plunger being shown in its retractedposition;

FIGURE 2 is an enlarged bottom view of the lampholder shown in FIGURE 1with the housing and plunger sectionalized to show the position of theplunger and springs when the plunger is in the retracted position;

FIGURE 3 is a bottom view corresponding to the View shown in FIGURE 2with the housing cut away to show the position of the plunger andsprings when the plunger is in an extended position;

FIGURE 4 is a fragmentary front elevational view of the lampholder shownin FIGURE 3;

FIGURE 5 is an exploded view of the lampholder;

FIGURE 6 is an enlarged view, partly in perspective and as seen from thegeneral direction indicated by the arrow 6 in FIGURE 3, of the slotformed in the plungerreceiving opening with the slot-engaging projectionbeing shown in section;

FIGURE 7 is a view corresponding to the view shown in FIGURE 6illustrating a modification of the configuration of the slot-engagingprojection and slot front end portion that can be employed in thepractice of another form of the invention;

FIGURE 8 is a view corresponding to the view shown in FIGURE 6illustrating another modification in the shape of the front end portionsof the slot and slot-engaging projection that can be utilized in thepractice of the invention; and 7 FIGURE 9 is a view, partly in section,illustrating still another modification in which an inclined surface isprovided at the front end portion of the slot and extends transverselyacross the slot.

Having more specific reference now to FIGURE 1 of the drawing, I haveillustrated therein a lampholder 10 embodying one form of my inventionand supporting the left end of a fluorescent lamp 11 of the bi-pin type.The lampholder 10 is supported on a bracket 12 attached to a supportmember 13 by screws 14, 15. The support member 13 may form the part ofthe lighting fixture or other surface on which it is desired to attachthe lampholder. It will be understood that the fluorescent lamp 11 Y isnormally supported at the other end by a lampholder (not shown) thatprovides 'a supprt for the right end 7,

of the lamp. 7

As is well known, the fluorescent lamp 11 is usually inserted into a setof two lampholders by first depressing a spring-biased plunger 16 intothe lampholder sufiiciently so that the right end of the fluorescentlamp 11 can then be inserted in the other lampholder (not shown).

It will be apparent that for a given lamp length a set of lampholdersmust be mounted and attached to a support in a predetermined spacedrelation.

Referring now more specifically to FIGURES 16, in j which like numeralshave been used to denote the corresponding parts in all of the figures,I will now more particularly describe the construction of the improvedlampholder 10 embodying one form of the invention. It will be seen thatlampholder 10 includes a housing 17 comprised of front and rear housingsections 18, 19 joined to form a unitary housing structure by a suitablesecuring means such as a rivet 20 (see FIGURE 4). When the housingsections 18, 19 are assembled, all of the component parts of thelampholder are located and locked in their proper assembled relation.The housing sections 18, 19 and the spring-biased plunger 16 are formedfrom any suitable insulating material such as phenolic orurea-formaldehyde resins.

As'is best seen in FIGURES 3, 4 and 5, the plunger 16 is essentiallycylindrical in shape and has a pair of opposed radially extending slotengaging projections or extensions 22, 23 integrally formed thereon. Theslot-engaging projections 22, 23 are slidably disposed in a pair ofopposed elongated slots 24, 25 to guide the travel of the plunger 16between its extended position (FIGURE. 3) and its retracted position(FIGURE 2). It will be seen in FIGURE 5 that when the housing sections18 and ends of the springs 33, 34 are biasingly; engaged with contactstrips 43, 44 at one end. At the other end the contact strips 43, 44(see FIGURE 5) provide pressure= lock terminal for external leads from afluorescent ballast.

or other power source. Since the contact strips 43, 44 and springs 33,34 are a part of the electrical circuit, they are formed from anysuitable electrically conductive material, such as an alloy of copper.

In FIGURE 6, I have illustrated a fragmentary portion of the lampholderhousing section 18 as viewed from the inside of the plunger-receivingopening 32. Also, shown in FIGURE 6 is a sectionalized view of theslot-engaging projection 22. .It will be appreciated that the front ends45, 46 (the. ends adjacent to the lamp) of both the opposed slotportions 26, 28, as seen in FIGURE 5, have essentially the same shape.Also, the pair of opposed slotengaging projections 22, 23 formedintegrally on the plunger 16 have essentially the same configuration.Thus, the description of the slot-engaging projection 22 and slotportion 26 is equally applicable to the other corresponding slot portionand slot-engaging projection.

An important feature of the present invention is the provision of aninclined surface 47 for engagement with the front end portion ofprojection 22. Preferably, the

angle of this inclined surface is selected to minimize the a It will beappreciated that when the plunger 16 is suddenly released from aretracted position, the slot-engag- 19 are assembled, the slot portions26, 27 and 28, 29 are 7 oined to form the pair of elongated slots '24and 25 respectively. The rear ends 30 of the slot portions 27, 29 (seeFIGURE 5) serve as a stop for the plunger 16 when it is pushed'to afully retracted position.

. The plunger 16 is biased outwardly through an opening contacts 35, 36.When the springs 33, 34 are compressedas shown'in FIGURE 2, the springs33, 34 bias the plunger 16 outwardly and also bias thecontacts 35, 36

outwardly from each other so that the contacts make a positive resilientconnection with lamp pins or inleads ;32- by means of a pair oflaterally spaced current conductf 37, 38. Asis best seen in FIGURE 2,thecontacts are" a formed with coined projections 39, 40 respectivelyand pivot aboutthe shoulders 41, 42 so that the springs-urge thecontacts 35,36 against the lamp inleads 37, 38, The

coined projections 39, 40 serve as a stop for the pivotal movement ofthe contacts 35, 36 when the plunger 16 is in the fully'extendedposition.

In order that an electrical connection be provided between the springs33, 34 and contact strips'43, 44, the

ing projection 22 will not generally travel precisely on thelongitudinal center line of theslot portion 26. Let

use assume that when the slot-engaging projection 22 initially strikesthe inclined surface of the slot, it is in the position shown in dashedoutline in FIGURE 6. When the impact part 48 strikes the inclinedsurface 47, it will glance off, and then the other impactjpart 49 willstrike the lower inclined. surface 50 of slot portion 26. The plungerbounces back and forth until it is finally seated in the fully extendedposition. I have found that such a plunger stop arrangement minimizesthe possibility of lampholder breakage. It will be understood that inthe embodiment of my invention, which I have illustrated in FIGURE 6,the surfaces 51, 52 formed on the frontend portion of slot-engagingprojection 22 are provided for the purpose of facilitating entry of theslot-engaging pro 7 jection into the slot portion 26. By way ofillustration of a another modification, I have shown in FIGURE 7 a frontend 53 of a slot-engaging projection 54 that is es-,

sentially squared off.

In the practice of the present invention, it will be understood that theinclined surface used to produce the desired deflections of'the plunger16 may be formed either on the slot or plunger. Animportant feature ofthe present invention is that the inclined surface, whether it is formedon the slot or plunger, is that it will cause the plunger initially tostrike the housing at. several points before it is seated in theextended position. a

In FIGURE 8 I have illustrated another modification of the slot-engagingprojection and slot wherein a pair of impact shoulders 54, 55 are formedat the front end of a slot portion 56 and a pair of inclined surfaces57, 58 are formed on a slot-engaging projection 59. Near the end of.another view of a section taken through a slot portion formed atvarious locations to achieve the desired results in accordance with theinvention. The angle of inclination of the surface with respect to thelongitudinal axis of the slot should be preferably less than 80 degreesand greater than degrees in order to minimize the impact force on thehousing section. Also, this angle of inclination should be greater thanthe friction and plastic locking angles of the insulating materials usedin the fabrication of the housing sections and the plunger in order toprevent the plunger from jamming into the housing section.

From the foregoing description it will be apparent that I have provideda lampholder construction utilizing an improved plunger stoparrangement. An important advantage of the improved arrangement is thatthe possibility of breakage is minimized when the spring loaded plungeris suddenly released from a retracted position. It was found that theuse of the impact deflecting surfaces to take up the impact forcessubstantially reduce the possibility of damage to the lampholder duringmanufacture and whenever the spring-loaded plungers are compressed andsuddenly released.

While I have described herein exemplifications of the invention whereinthe slot-engaging projections were formed on lampholder plungers, itwill be apparent to those skilled in the art that, for example, theslot-engaging projections may be formed in the plunger-receiving openingof the lampholder housing and that the slots may be formed in theplunger. Also, it will be apparent that the inclined surface need not beplanar but may be, for example, conical in shape. Thus, it will beunderstood that various other changes and modifications may be madewithout departing from the invention. It is therefore intended in thefollowing claims to cover all such equivalent variations as come withinthe true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A lampholder for an electric discharge lamp, said lampholdercomprising a housing having a plunger-receiving opening formed therein,a retractable plunger slidably mounted in said plunger-receivingopening, a pair of spaced contacts mounted in a wall of said plunger andmovable relative to said plunger, terminal means for providingconnections with external electrical leads, a pair of current conductingsprings in said housing, one end of said current conducting springsengaging said' contacts to bias said contacts pivotally and to bias saidplunger outwardly of said plunger-receiving opening from a retractedposition to an extended position, means at the other end of said springsfor providing an electrical connection between the current conductingsprings and said terminal means, at least a pair of oppositely disposedelongated slots formed in said housing and extending toward saidplunger-receiving opening for guiding the movement of said retractableplunger between said retracted and extended positions, a pair ofslot-engaging projections formed on said plunger and extending into saidelongated slots, each of said slot-engaging projections having an impactmember formed at the front ends thereof, each of said elongated slotsformed with at least one surface generally inclined relative to thedirection of movement of said slot-engaging projection and engageablewith said surface to deflect the movement of the members of saidslot-engaging projections when the lampholder is near the end of itstravel to the extended position.

2. A lampholder for an electric discharge lamp having at least oneinlead for energization from an electrical current source, saidlampholder comprising a housing of insulating material including aplunger-receiving member with an opening formed therein, a retractableplunger slidably mounted in the opening of said plunger-receiving memberfor movement between an extended position and a retracted position,spring means disposed between said retractable plunger member and saidhousing to cause said plunger member to be biased to the extendedposition, contact means carried on said plunger member, one of saidmembers having a pair of elongated slots, the other of said membershaving formed thereon slot-engaging projections extending into saidelongated slots for guiding the travel of said plunger member betweenextended and retracted positions, each of said slots and saidslot-engaging projections having a front end portion, one of said frontend portions having at least one surface generally inclined relative tothe direction of movement of the retractable plunger member, the otherfront end portion having an impact part associated with one of saidinclined surfaces, whereby when the plunger member is released from theretracted position, normally one of the impact parts strikes theinclined surface associated therewith to cause a first deflection ofsaid plunger member to change and to cause another impact part to strikethe inclined surface associated with it and cause at least a seconddeflection of said plunger member before said plunger member is seatedin the extended position.

3. The lampholder set forth in claim 2 wherein the sloten gagingprojections are formed in said retractable plunger member and saidelongated slots are formed in said plunger-receiving member.

4. The lampholder set forth in claim 2 wherein each front end portion ofthe slot-engaging projections includes a pair of spaced inclinedsurfaces.

5. The lampholder set forth in claim 2 wherein the inclined surface hasan angle of inclination of not less than 10 degrees and not more thandegrees with respect to the longitudinal axis of the elongated slot.

6. A lampholder for a fluorescent lamp having at least one inlead forenergization from a power supply, a said lampholder comprising aninsulating housing formed with a plunger-receiving member having an openend, a hollow contact support member slidably mounted in saidplunger-receiving member for movement between a retracted position andan extended position, said contact support member extending through theopen end of said housing when in the extended position, spring meansdisposed between the hollow cont-act support member and the housing tonormally cause said hollow contact support member to be biased to theextended position, contact means carried in said hollow contact supportmember for engagement with an inlead of the fluorescent lamp, one ofsaid members having a pair of elongated slots formed thereon, the otherof said members having a pair of slot-engaging projections engaged insaid elonated slots for guiding the movement of the contact supportmember from a retracted position to the extended position, each of saidelongated slots and said slot-engaging projections having a front endportion, one of said front end portions formed with at least one slantedsurface inclined with respect to the direction of travel of the slotengaging projection, and the other front end portion associatedtherewith having an impact part aligned with one of said slantedsurfaces to cause the hollow contact support member to be deflected backand forth before the contact support member is seated in the extendedposition after being released from a retracted position.

7. The lampholder set forth in claim 6 wherein said slot-engagingprojections are formed on said plunger-receiving member and saidslot-engaging projections are a formed in the plunger-receiving member.

8. The lampholder set forth in claim 6 wherein said slanted Surfaceshave an angle of inclination with respect to the general line ofdirection of the contact support member that is not less than 10 degreesand not more than 80 degrees.

'9. A lampholder for an electric discharge lamp having at least oneinlead for energization source of electrical current, said lampholdercomprising an openended insulating housing having a plunger-receivingmember, a hollow contact support member slidably mounted in saidplunger-receiving member, contact means carried on said hollow contactsupport member for engagement with 'an inlead of the electric dischargelamp, at least a pair of slot-engaging extensions formed on one of saidmembers, at least a pair of elongated slots formed on the other of saidmembers and extending generally along a longitudinal axis, saidslot-engaging extensions'being movably disposed in the slots formed inthe said ,other member to slidably guide the hollow contact supportmember between a retracted position and an extended position, springmeans supported between said housing and said hollow contact supportmember to bias said hollow contact support member outwardly toward theextended position, each of said elongated slots and said slot-engagingextensions having a front end portion, one of said front end portionshaving an impact part and the other of said front end portions having aslanted surface for engagement with the associated impact part, saidimpact part striking said slanted surface to deflect the movement of thehollow contact support member when it is near the end of its travel tothe extended position thereby tot minimize the a resulting impact.

10. The lampholder set forth in claim9 wherein at least one of saidslanted/surfaces has an angle of inclination of not less than 10 degreesand not greater than 80 degrees with respect to the longitudinal axis ofsaid elongated slot associated therewith.

' 11. A lampholder for a fluorescent lamp having at least low movablecontact support member slidably mounted in said plunger-receiving memberfor movement between a retracted position and an extended position, saidmovable contact support member extending through saidopen' end of saidhousing when in the extended position, spring means disposed between thehollow movable contact support member and the housing to normally biassaid movable contact support member to the extended position, contactmeans carried by the movable contact support mem-' ber and engageablewith an inlead of a fluorescent lamp, said movable contact supportmember having a projection extending circumferentially over at least aportion of said support member, said projection having a front endportion, said plunger-receiving member having a slanted sur-- faceinclined with respect to the direction of travel of said front endportion of the projection, said slanted surface having an angle ofinclination with respectto said direction of travel that is not lessthan 10 degrees and not more than degrees, and said slanted surfacebeing engageable with said front end portion of said projection when themovable contact support member is returned to the extended position tocause said plunger-receiving member to be deflected at least once beforethe plunger-receiving member is seated in the extended position.

7 References Cited UNIT ED STATES PATENTS 2,651,024 9/1953 Miller .V33945 2,883,639 4/1959 Kulka 339, ss. 2,977,563 3/1961 Lennox 339 ssMARVIN A. CHAMPION, Primary Examiner.

I. H. MCGLYNN, Assistant Examiner.

1. A LAMPHOLDER FOR AN ELECTRIC DISCHARGE LAMP, SAID LAMPHOLDER COMPRISING A HOUSING HAVING A PLUNGER-RECEIVING OPENING FORMED THEREIN, A RETRACTABLE PLUNGER SLIDABLY MOUNTED IN SAID PLUNGER-RECEIVING OPENING, A PAIR OF SPACED CONTACTS MOUNTED IN A WALL OF SAID PLUNGER AND MOVABLE RELATIVE TO SAID PLUNGER, TERMINAL MEANS FOR PROVIDING CONNECTIONS WITH EXTERNAL ELECTRICAL LEADS, A PAIR OF CURRENT CONDUCTING SPRINGS IN SAID HOUSING, ONE END OF SAID CURRENT CONDUCTING SPRINGS ENGAGING SAID CONTACTS TO BIAS SAID CONTACTS PIVOTALLY AND TO BIAS SAID PLUNGER OUTWARDLY OF SAID PLUNGER-RECEIVING OPENING FROM A RETRACTED POSITION TO AN EXTENDED POSITION, MEANS AT THE OTHER END OF SAID SPRINGS FOR PROVIDING AN ELECTRICAL CONNECTION BETWEEN THE CURRENT CONDUCTING SPRINGS AND SAID TERMINAL MEANS, AT LEAST A PAIR OF OPPOSITELY DISPOSED ELONGATED SLOTS FORMED IN SAID HOUSING AND EXTENDING TOWARD SAID PLUNGER-RECEIVING OPENING FOR GUIDING THE MOVEMENT OF SAID RETRACTABLE PLUNGER BETWEEN SAID RETRACTED AND EXTENDED POSITIONS, A PAIR OF SLOT-ENGAGING PROJECTIONS FORMED ON SAID PLUNGER AND EXTENDING INTO SAID ELONGATED SLOTS, EACH OF SAID SLOT-ENGAGING PROJECTIONS HAVING AN IMPACT MEMBER FORMED AT THE FRONT ENDS THEREOF, EACH OF SAID ELONGATED SLOTS FORMED WITH AT LEAST ONE SURFACE GENERALLY INCLINED RELATIVE TO THE DIRECTION OF MOVEMENT OF SAID SLOT-ENGAGING PROJECTION AND ENGAGEABLE WITH SAID SURFACE TO DEFLECT THE MOVEMENT OF THE MEMBERS OF SAID SLOT-ENGAGING PROJECTIONS WHEN THE LAMPHOLDER IS NEAR THE END OF ITS TRAVEL TO THE EXTENDED POSITION. 